NAME

Image::Timeline - Create GIF or PNG timelines

SYNOPSIS

      use Image::Timeline;
      my $t = new Image::Timeline(width => 400);
      $t->add('J.S. Bach', 1685, 1750);
      $t->add('Beethoven', 1770, 1827);
      $t->add('Brahms',    1833, 1897);
      $t->add('Ravel',     1875, 1937);
      ...
       # For older versions of GD:
      $t->write_gif('composers.gif');
       # For newer versions of GD:
      $t->write_png('composers.png');
  
      # Get the GD object
      my $img = $t->draw;

DESCRIPTION

This module creates bar-format timelines using the GD.pm module. Depending on the version of GD you have, you can produce either GIF or PNG files.

See the file `t/truth.gif' for example output.

METHODS
new()

Creates a new timeline object. Accepts several named parameters that affect how the timeline is created:

• width How many pixels wide the image should be. Default is 900 pixels, for no good reason.
• font Which GD font should be used to label each entry in the timeline. Default is `gdTinyFont'.
• bar_stepsize The "tick interval" on the timeline's legend at the top. Default is 50 (i.e. 50 years).
• vspacing How many pixels of vertical space should be left between entries. Default is 2.
• hmargin How many pixels should be left at the far right and far left of the image. Default is 3.
• bg_color
• bar_color
• endcap_color
• legend_color
• text_color These parameters affect the colors of the image. Each associated value should be a 3-element array reference, specifying RGB values from 0 to 255. For instance, the default value of `bar_color' is pure red, specified as `[255,0,0]'. The defaults are reasonable, but not necessarily attractive.

add(label, start, end)

Adds a new entry to the timeline. Supply a label that you want to include in the image, the starting date, and the ending date.

draw()

Creates the `GD' object and returns it. This method is where all the real work is done - the code must figure out things like how to squeeze the entries most compactly but avoid collisions between bars, when to draw labels above their bars and when below (again, to avoid collisions between labels), the image's height (a function of how many concurrent entries it contains), and so on.

write_png(filename)

write_gif(filename)

A convenience method which writes the timeline to a file. Because of some Unisys/Compuserve/GD patent issues that I don't want to get involved in, writing PNG output requires a version of GD newer than 1.19, while writing GIF output requires GD version 1.19 or older.

LIMITATIONS

Currently all dates/times are specified as integers, which are meant to represent years. Finer granularity (time of day) isn't supported yet, but it probably could be if it's desired (or someone gives me a patch).

Doesn't yet fully test the PNG capabilities during 'make test'. This is just because I haven't yet found time to build all the necessary PNG libraries on my system, so I haven't gotten the benchmark image built. Please let me know whether this works correctly, and maybe even send me the 't/testdata.png' file created so I can include it here.

AUTHOR

Ken Williams, ken@forum.swarthmore.edu

COPYRIGHT

Copyright 2001 Ken Williams. All rights reserved.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

SEE ALSO

perl(1), GD(3)